What blood pressure counts as high, and when do you need to start medication?

What counts as high

Home readings run slightly lower than clinic readings, so the home threshold is 135/85. A high clinic reading with normal home readings is called white-coat hypertension; it is common and does not need medication yet, but it should be followed because a proportion of people go on to develop sustained hypertension.

How to measure so the numbers can be trusted

• Sit and rest for 5 minutes first. No coffee, smoking or exercise in the 30 minutes before, and empty your bladder.
• Sit with your back supported, feet flat, arm resting on a table with the cuff at heart level. Do not talk during the reading.
• Take 2 readings 1 minute apart and use the average; take a third if they differ a lot.
• At home, measure morning and evening for 7 consecutive days before your appointment, discard day 1, and bring the average to the doctor.
• Use a validated automatic upper-arm monitor. Wrist monitors are more easily inaccurate.

Good to know: A single reading taken while stressed, in pain or short of sleep is not a diagnosis. If your first reading is high, repeat at home as above and bring the results for assessment.

When medication is needed

The doctor looks at the blood pressure number together with your overall cardiovascular risk: age, diabetes, high cholesterol, smoking, kidney disease, and any sign that organs are already affected, such as protein in the urine or a thickened left ventricle.

At grade 1 (140–159/90–99) with none of these, the guideline allows 3–6 months of serious lifestyle change before re-measuring, starting medication only if it has not come down. But with diabetes, kidney disease, previous heart disease or stroke, or high overall risk, doctors usually start medication from the outset alongside lifestyle change, because waiting is not worth it.

From grade 2 (≥160/100) medication starts without waiting for lifestyle results, because lifestyle alone is unlikely to bring it to target and the risk while waiting is high.

The target once treated

The general target is below 140/90, and if well tolerated current guidelines recommend going to below 130/80, especially for people under 65, with diabetes or with kidney disease. For the very elderly or anyone who gets dizzy when pressure falls, the doctor may set a gentler target. Your doctor will agree a target with you.

Lifestyle changes that lower blood pressure

The main sodium source in a Thai diet is not table salt but fish sauce, soy sauce, seasoning powder, instant noodles, processed food and dipping sauces. Halving these has a clearer effect than simply not adding salt.

Signs that mean the emergency room, not an appointment

• Blood pressure ≥180/120 together with severe headache, chest pain, breathlessness, blurred vision, slurred speech, weakness of an arm or leg, or confusion
• Very high blood pressure in pregnancy, especially with swelling, headache or visual disturbance

Good to know: ≥180/120 without symptoms does not need the emergency room but should be seen by a doctor within 1–2 days. Do not buy blood pressure tablets to bring it down quickly yourself. Lowering it too fast is just as dangerous.

Blood pressure care at the clinic

Mongkhondee Clinic diagnoses, starts treatment and follows hypertension long term. The doctor reviews your home readings, orders kidney and lipid blood tests on schedule, and adjusts medication to suit you. See chronic condition care. If you are treated elsewhere and want to collect your medication closer to home, read Can I transfer my diabetes or blood pressure care to the clinic?. And because blood pressure usually travels with cholesterol, read LDL and HDL: what is normal.